Metal can bodies, such as steel cans and aluminum cans, have lighter weight and higher shock resistance, have better storage properties and sealing properties, and are also more easily recycled and reused than glass bottles. Therefore, they are heavily used and used for various purposes as containers for food or drink storage, particularly as containers for soft drinks, such as soda pop, luxury drinks, such as coffee, or alcoholic drinks, such as beer, as in plastic containers.
Characters and a design are printed on the surface of the barrel portion of these can body containers to indicate the packed contents of a commercial product, a trade name, and the like, and also increase consumers' willingness to purchase the product. In order to attract the attention of consumers and promote sales, a design and ornamentation, the so-called decoration, on the surface of the barrel portion of a commercial product can body are regarded as important. Recently, particularly, decoration in which the can body of a commercial product is conspicuous and which is aesthetic and has an impact (is impressive) to obtain a high grade feel and the favor of purchasers has become more important.
Therefore, previously, an ornamental pattern has been directly printed on the barrel portion of a can body, or a resin film on which a pattern is printed has been attached to the barrel portion of a can body. But, clear printing on a cylinder surface is difficult due to curved surface printing, and even if a printed film is simply wound and attached around a barrel portion, simple ornamentation without elegance is provided. In addition, in metal can bodies, generally, specular gloss is regarded as important as an aesthetic design, and in aluminum cans, the bright and brilliant metal color of the metal is used for a design effect as the background (base) of an ornamental pattern.
In seamless cans formed by drawing, drawing and ironing, or stretch-drawing an aluminum alloy plate or a steel plate, the side wall is subjected to severe processing, and therefore, surface roughness occurs, and the specular gloss is insufficient. In aluminum cans, the metal color is relatively excellent, but better specular properties may be desired. In addition, particularly for seamless cans formed from a resin-coated metal plate in which a polyester film or the like is laminated, in both aluminum cans and steel cans, the forming is such that the metal surface does not come into direct contact with the forming tool. Therefore, the surface roughness of the metal surface under the resin is larger, and specular gloss has not been obtained. In welded cans, specular gloss cans have been made by making the degree of surface roughness of a tin-plated steel plate very small, but a problem has been that such a surface is easily scratched due to conveyance during can production, and the like.
In steel cans that are more inexpensive than aluminum cans, specular gloss like that of aluminum cans is not obtained, and a dull grayish metal color is obtained. Therefore, attempts are made to exhibit specular gloss by applying a bright metal powder paint to the barrel portion of the can body, or attaching a resin film, on which gravure printing with metal-like gloss is provided by a silver ink, to the barrel portion of the can body. But, it is difficult to obtain sufficiently bright, brilliant specular gloss.
There is also a gravure ink containing vapor-deposited aluminum as a pigment. But, in a case where printing is performed with the gravure ink, even if a metallic feel appears, the aluminum pigment whitens when the can body is subjected to retort treatment, and therefore, the gloss decreases.
Accordingly, an attempt to exhibit a high-grade specular gloss feel by attaching a brilliant metal foil or vapor-deposited metal layer, such as aluminum, to the surface of the barrel portion of a metal can body, such as a steel can, is also proposed (Patent Document 1), but a deep high-grade specular gloss feel is not obtained.
Recently, can bodies in which a metal foil or a vapor-deposited metal layer and a transparent resin film on which a pattern is printed are combined and laminated on the barrel portion of a can body to provide decoration with a deep ornamental pattern and metal gloss have been disclosed (Patent Documents 2 to 4).
Such decorative can bodies are expected to provide high-grade decoration even in steel cans due to the correlation between a deep ornamental pattern and brilliant specular gloss. But, even in experimental production, many blisters (fine protrusions) occur in the ornamental surface, and thus, no specular gloss appears, and beautiful and brilliant specular gloss ornamentation is not obtained.    Patent Document 1: Japanese Patent Laid-Open No. 2000-229642 (see Abstract)    Patent Document 2: Japanese Patent Laid-Open No. 2000-95248 (see Abstract and FIG. 2 (C))    Patent Document 3: Japanese Patent Laid-Open No. 2005-1676 (see Abstract and FIG. 6)    Patent Document 4: Japanese Patent Laid-Open No. 2005-206160 (see Abstract)